Kamla Devi was Rajasthan's first woman to graduate from Barefoot college as a solar engineer. Photograph: Suzanne Lee/Panos

Securing the end of her bright yellow and orange sari firmly around her head, Santosh Devi climbs up to the rooftop of her house to clean her solar panels. The shining, mirrored panels, which she installed herself last year, are a striking sight against the simple one-storey homes of her village. No less remarkable is that this 19-year-old, semi-literate woman from the backwaters of Rajasthan has broken through India's rigid caste system to become the country's first Dalit solar engineer.

While differences of caste have begun to blur in the cities, in rural India Dalits – also known as "untouchables" – are still impoverished and widely discriminated against.

Growing up, Santosh had to avoid the upper caste people of her village or cover her face in their presence. Nowadays, they seek her help. "For them, I am a solar engineer who can repair and install the light installations," she says. "From looking down on the ground when higher caste people passed to looking them in the eye, I never imagined this would have been possible."

Santosh trained to be a solar engineer at the Barefoot College in Tilonia, 100km from Jaipur. The college was set up in 1972 by Sanjit "Bunker" Roy to teach rural people skills with which they could transform their villages, regardless of gender, caste, ethnicity, age or schooling. The college claims to have trained 15,000 women in skills including solar engineering, healthcare and water testing. Roy, 65, says his approach – low cost, decentralised and community driven – works by "capitalising on the resources already present in the villages".

The college, spread over eight acres, runs entirely on solar energy, maintained by the Barefoot solar engineers. Since the solar course was launched in 2005, more than 300 Barefoot engineers have brought power to more than 13,000 homes across India. A further 6,000 households, in more than 120 villages in 24 countries from Afghanistan to Uganda, have been powered on the same model.

Only villages that are inaccessible, remote and non-electrified are considered for solar power. A drop in the ocean, perhaps – 44% of rural households in India have no electricity – but these women are making an important contribution to the nation's power needs. Rural India, comprising 72% of the population, continues to depend on fossil fuels, which will be a setback for the country's environmental goals unless the government is able to transfer this dependence to renewable sources.

In India, Roy's engineers already save at least 1.5m litres of kerosene a year, which would otherwise have been used to power lamps and stoves, according to Bhagwat Nandan, the co-ordinator of the college's solar division.

Marked by a stick fence, Santosh's predominantly Dalit village, Balaji Ki Dhani, is a hamlet consisting of about 20 mud houses scattered over five acres of semi-arid land. The only incongruous element in what could otherwise pass as an 18th-century rural set-up is the cement-built home – the only one in the village – where Santosh lives with her husband, baby son and in-laws. The house has two bedrooms, two mud huts in the courtyard – one housing goats, the other a kitchen – and a third room that functions as Santosh's workshop. Here she spends around six hours a day repairing solar lanterns.

Santosh built the house with money she made as a solar engineer. Thanks to her, the other households in the village now have solar power too. Under the Barefoot model, they pay a monthly fee based on how much they would have spent on kerosene, batteries, wood and candles. Some of the money goes towards the solar engineer's monthly stipend, while the rest pays for components and spare parts.

Choti Devi, an upper caste Hindu in her late 60s, is Santosh's immediate neighbour. She can't stop gushing about her solar lanterns. "With the light, it is easier to make the beds at night. During the rainy season many poisonous insects roam around, but now that we have light in the night we do not worry as much. The lanterns have also helped us to guard our cattle properly while getting them back to the house in the evenings," she says.

As is the custom in rural India, women do the bulk of the housework and agricultural labour. Although Santosh doesn't work in the fields any more, at home she is endlessly busy. If she is not tending to her 17-month-old son, she is milking the cattle, feeding the livestock, attending to customers at the small grocery store she runs from home and repairing solar lanterns. She is quick-witted and confident, although she admits the first day at college was scary.

"I thought I would never be able to understand anything – let alone be able to do it on my own. I didn't even know that we could use the sunlight to light up our homes at night ... I was as amazed as the other villagers."

Since she became a Barefoot solar engineer, the total income of the family has doubled. "Before, I worked in the fields the whole day and then I had to rush back so that I could cook dinner while there was still daylight. I hardly got a moment to breathe," says Santosh.

At the Barefoot College, the women learn through listening and memorising, using colour-coded charts that help them to remember the permutation and combination of the wires without needing to read or write.

Nomad Santra Banjara poses with a solar lantern made at the Barefoot College. Photograph: Suzanne Lee/Panos

The model is being replicated in Africa, Latin America and south Asia. The first batch of Barefoot engineers from Tanzania, Uganda, Gambia, Malawi, Ethiopia, Sierra Leone, Rwanda and Bhutan completed their six-month residential training at Tilonia between 2008 and 2009, and have since set up solar power in their villages.

Any woman over 35 from a remote, inaccessible, non-electrified area can enrol for the international course, provided she is backed by her village. As Roy says: "It makes sense to choose women, especially older women, as they are more loyal to their roots and less impatient to try out new pastures, which men are wont to do as soon as they are given a certificate."

Precious Molobane Mamogale, 42, a mother of four who lives in a village around 500km from Johannesburg in South Africa, is frowning in concentration at a circuit board in one of the college workshops. She looks uncomfortable. "I didn't expect India to be so hot," she says. However, despite the conditions and the vegetarian diet, she is full of hope for the future. "I want to go back to my country and bring light to my province – and want to open a college like this there so that I can train more women," she explains. Back home, Precious was unemployed and survived on state benefits that she received for her last two children; "not enough to feed a family of six", she says. Her husband sometimes earned money by working as a taxi driver in the nearest town. When she heard about the course, she was immediately attracted by the opportunity to learn something of benefit to her community and to the family coffers.

The class is conducted in a large, rectangular workshop, with a long worktable running through the middle, around which the women sit with their individual colour sheets and panels. Neat rows of solar lanterns line shelves, while charts detailing the colour codes hang on the walls and flutter in the breeze of the fan. The room is airy, but the heat, even at 10am, scorches the ground outside.

Guman Singh, their short, bespectacled teacher, calls the women to the blackboard to read out the colour codes. One of them uses her knowledge of English to help her compatriots learn the words for the colours in their local language. "It is always very difficult in the beginning. Sometimes we feel like tearing our hair in frustration," Singh says. "But once they start getting the colour codes it is easy. We also teach them through sign language and practical demonstrations."

Further down the long table, Matildah Chikwata, 43, from a village in Zimbabwe, grapples with the workings of a solar panel. Back home she was a vegetable seller, earning around $5 a day. "We could afford nothing – not even taking the vegetables to sell at the nearest town, so we depended on the villagers coming to buy from us," she says. "People here are poor too. But they are using their hands to make their lives better. I want to go back home and teach people to use their hands. If I can learn at this age, so can anyone."

Back in Balaji Ki Dhani, Santosh climbs down from her roof and reflects on her modest ambitions for her family: a television, a grinder to make flour, and a motorbike for her husband, who has to walk the 10km to work every day. With her livelihood secure thanks to her training, these small luxuries are now within reach. "I never thought I would be able to do anything worthwhile," she says proudly.